Stereoscopic x-ray system.



H. 0. SNOOK & E. W. KELLY.

smmoscomo X-RAY SYSTEM. APPLICATION FILED AUG. 15, 1912.

1,123,942. Patented Jan. 5, 1915.

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STEEEOSGOPIO X-RAY SYSTEM.

APPLICATION FILED AUG. 15, 1912.

Patented Jan 5,1915.

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HOMER CLYDE SNOOK, OF CYNWYD, AND EDWIN W. KELLY, 0F PHILADELPHIA, PENNSYLVANIA.

STEREOSCOFIC X-RAY SYSTEM.

Specification of Letters Patent.

Patented Jan. 5, 1915.

Application filed August 15, 1912. Serial No. 715,161.

To all whom it may concern:

Be it known that we, HOMER CLYDE SNOOK and EDWIN W. KELLY, citizens of the United States, of Cynwyd and Philadelphia, State of Pennsylvania, have invented new and useful Improvements in Stereoscopic X-Ray Systems, of which the following is a specification.

Our invention relates to a system of and apparatus for causing the production of X-rays from a plurality of anti-cathodes disposed either within one X-ray tube, or in separate'X-ray tubes.

()ur invention resides in a system of the character above referred to adapted for stereoscopic X-ray purposes, whereby an ob server may see, by .aid of X-rays, ob ects appearing in images in stereoscopic relation, that is, whereby an observer may see an object not in an image consisting of a simple projection of the object, but in imagw so related that the effect upon the observer is the same as if he were viewing the object with both eyes simultaneously.

Our invention resides also inmeans for insuring equality in intensity andcharacter of the X-rays produced at the different anti-cathodes, or for controlling these intensities with respect to each other in any desired manner.

Our invention is applicable not only to a stereoscopic X-ray system but to any system involving the use of a plurality of X- ray tubes, or a tube having a plurality of anti-cathodes, of a plurality of other similar translating devices, for whatever use intended; and in the case of the use of a plurality of X-ray tubes for the destruction of germs, larvae, or the like in or upon to bacco or other substance.

Our invention resides in the system and apparatus hereinafter described and claimed. For an illustration of some of the forms our invention may take, reference is to be had to the accompanying drawings, in which: i

Figure 1 is an illustration, partly diagrammatic, of an application of our system and apparatus for stereoscopically viewing objects by the aid of X-rays. Fig. 2 is a graphic representation of a mode of use of the current waves. Fig. 3 is an illustration is a representation of a shutter suitable for use in connection with a system such as illustrated in Fig. 1. Fig. 5 is an end view of switching or commutating means illustrated in Fig. 1. Fig. 6 is a view, partly diagrammatic, of the application of our invention in a rectifying system for stereoscopic X-ray observation. Fig. 6 is an end elevational view of a part of the rectifying apparatus of Fig. 6. Fig. 7 is a view of a shutter suitable for use in connection with the apparatus of Fig. 6. Fig. 8 is a view of a modified form of shutter adaptable for use in connection with the apparatus of Fig. 6'. Fig. 9 is a diagrammatic view illustrating a form our invention may take. Fig. 10 is a diagrammatic view showing a further form our invention may take.

Referring to Fig. l, a motor-generator G comprises a two pole field in which rotates the armature A having the direct current to the slip rings 10 and 11, insulated from each other and communicatin respectively with brushes 12 and 13, communicating with the reversing switch 14. From one terminal of the reversing switch 14 connection is made with the primarv P, adjustable, if desired, as to the number of its turns, of a step-up transformer T whose secondary winding is S. The other terminal of the primary P is connected with the brush 15 bearing upon the circumferentially continuous slip ring 16 with which are electrically connected the commutator segments 17 and 18, these segments having relatively short circumferential extent. In the path of "travel of the contact 17 is disposed the brush 19 adapted to engage said contact 17, the

brush 19. communicating with the other terring 16, contacts 17 and 18, is secured upon the armature shaft 23 and rotates in fixed relation with respect to the armature.

One terminalof the secondary S connects with the brush 2i bearing upon the hub 25 of the rotating conductor 26, the hub 25 being insulated from the shaft 27, as indicated in Fig. 5, the shaft 27 being an extension of the armature shaft 23, or being a shaft rotating in synchronism or definite relation with the armature shaft 23. The outer end of the conductor 26, in its rotation, comes close to the stationary conducting arcs 28 and 29 which are of substantially the same angular extent as the contacts 17 and 18. The M028 is connected with the cathode 30 of an X-ray tube X and the conducting are 29 is connected with the anode 33 of a second X-ray tube X The anode 32 ofthe tube X and the cathode 31 of tube X are connected together and to the other terminal of the secondary S.

A fluorescent scneen 34 is disposed in front of the anodes 32 and 33, the object 35, to be viewed, intervening between these targets or anodes and the screen 34. A. rotating shutter 36 is disposed in front of the fluorescent screen 34 and is driven in fixed relation withthe shaft 23 by the flexible shaft 37, or any other suitable means. The shutter 36, as seen in Fig. 4, has an are shaped aperture 38, of width suitable to accommodate suitable vision by a human eye and ,of an angular extent substantially equal to the angular extent of the arcs 28 and 29 and the contacts 17 and 18. The position of the eyes of the observer are indicated in Fig. 1, 39 representing the left eye and 40 representing the right eye.

The operation is as follows: Upon closure of the switch 7 the motor-generator G starts and is brought up to suitable speed by cutting out more or less of the resistance 5. The minimum speed is that which will produce a succession of images on the screen 34 such that the persistence of vision will not cause the alternate images, as viewed through the shutter 36, to be separate and distinct images, or such that the impression made by one image does not disappear be fore the appearance of the other image. Vith the motor-generator running at the desired speed there is impressed upon the slip rings 10 and 11 and brushes 12 and 13 an alternating potential. The circuit through the primary P is closed alternately through contact 17, brush 19 and contact 18 and brush 2-1, current being delivered through the primary P not during an entire potential or electro-motive-force wave, but only during a portion thereof, as indicated ir Fig. 2, where the curved dotted line 41 represents a positive wave and the dotted line 42 a negative wave. The contact 17, for example, allows current to flow through the primary 1? only during the time represented by the distance 43, the area 44 within the solid lines representing the amount and duration of the current energy passed through the primary P. After a further half revolution of the shaft 23 the contact 18 comes into engagement with brush 21 and there flows through the primary P, but in opposite direction, energy represented by the area 45 taken from the negative half wave 42. Assuming the parts momentarily in the position indicated in Fig. 1, energy is flowing through the primary P from contact 18 and brush 21 and from the secondary S to the anode 32 of tube X to the cathode 30, are 28, across the small gap to the conductor 26 through brush 24: to the other terminal of the secondary S. The connections aresuch that the anode 32 is positive and the cathode 30 negative. X-rays will now be produced by tube X and produce an image on the screen 34 which is seen by the left eye 39 through aperture 38. At a half revolution later of the shaft 23 the primary P will be energized through contact 17 and brush 19 and the tube X will have its anode 33 brought into circuit through are 29 and the conductor 26 which will then be in the dotted position, energy flowing between cathode 31 and anode 33 to the other terminal of the secondary S. X-rays will now be produced by the tube X and, the shutter 36 having made a half revolution also, the aperture 38 will be in front of the right eye 40 which will see the image on screen 3& produced by tube X These images are produced alternatelv and at such high speed that they are viewed separately by the left and right eves but,

due'to the persistence of vision, the effect upon the observer is the same as if he were viewing the object 35 continuously with both eyes, thus seeing all parts, as it were. in their true relations with respect to each other, and just 'as any obiect visible under ordinary light is seen by both eyes.

Instead of using two separate tubes X and X ,'as indicated in Fig. 1, a single tube X such as shown in Fig. 3 may be employed. Here the anode 32 and cathode 31 are combined and are connected to one terminal of the secondary S; and the other cathode 30 connected with the arc 2S and the other anode 33 connected with the are 29. The principle is the same, but here all the anodes and cathodes are disposed within one tube within the same vacuum. Vith whatever care the tubes X .4 or X are made, the dielectric cohesion between one anode and cathode will be different from the dielectric cohesion between the other anode and its cathode, whether within the same or separate tubesjso that different potentials will have to be impressed upon the different pairs of anodes and cathodes in order that X-rays of the same intensities and characteristics shall be produced by both in order to produce images on the screen 34 of like intensities or of like clearness. Indeed with proposed forms of X-ray stereoscopic apparatus this defect has been so great as to cause the alternate images viewed alternately by the two eyes to be so different in definition, intensity, etc., as to produce a very imperfect effect upon the observer. To overcome this defect we employ the commutator having the contacts 17 and 18 and the adjustable resistances 20 and 22. The

tube X is supplied with energy derived through the resistance 22 and the tube X is rection for one tube, and in the opposite direction for the other tube. By the arrangement shown in Fig. 6 however the high tension alternating current is rectified, as will presently appear. represents a motor-generator, in' this case however, having four field poles. Upon the slip rings 10 and 11 is impressed an alter-. nating potential or electro-motlve-force,

' and through brushes 12 and 13, connection is made to reversing switch 14. The primary P of the step-up transformer T, having secondary S, is preferably adjustable as to its number of turns and has one terminal connected with one terminal of the reversing switch 14. The other terminal of the primary P connects with brush 15 bearing upon the circumferentially', continuous slip ring 16. The commutator contacts 46 and 47 are disposed at opposite ends of a diameter and come in succession into communication with the brush 48 communicating through the adjustable resistance 49 with the other terminal of the reversing switch 14. Two similar contacts 50, one invisible in Fig. 6, disposed at-opposite ends of a diameter, and at 90 with respect to the contacts 46 and 47, come into communication with the brush 51 communicating through an adjustable resistance 52 with the same remaining terminal ofthe reversing switch 14. All the contacts 46, 47 and 50, 50 are electrically connected with the slip ring 16. One terminal of thesecondary S connects with the two supply arcs 53 and 54 and the other terminal of the secondary S connects with the two supply arcs 55 and 56. Opposed to these four supply arcs are In this figure G the distributing arcs 57, 58, 59 and 60, respectively. The arcs 57 and 60 connect with the cathodes 61 and 62, respectively, of the X-ray tube X having the double anode or target 63 connected to distributing arcs 58- and 59. Cotiperating with arcs 53 and 57 is the rotating cross-connector 64; with arcs 54 and 58 cotiperates the crossconnector 65; with the arcs 55 and 59 cooperates the cross-connector 66; and with the arcs 56-and 60 coiiperates the cross-connector 67. The cross-connectors 65 and 67 are disposed at right angles with respect to the cross-connectors 64 and 66, all these cross-connectors being insulated from each other and rotated by the shaft 68, of wood or other insulating material, secured to and rotated by the armature shaft 23. The angular extent of the arcs and the relation of the cross-connectors is indicated in Fig. 6 Secured to the shaft 23 is the flexible shaft 37 which rotates the shutter 69 in definite relation and at the same rate with the shaft 23. This shutter has four apertures 70, 71, 72 and 73, the apertures 70 and 72 beingat a radial distance from apertures 71 and 73 corresponding with the distance between the human eves, substantially two and one-half inches, this being the distance also between the targets or anodes of tube X*. The fluorescent screen and the object to be viewed are omitted from Fig. 6 but they are disposed in the relation indicated in Fig. 1 between the targets and the shutter. As indicated in Fig. 8 the shutter 69 is similar to the shutter 69 of Fig. 7 except that it maybe smaller because the radial distance between the apertures 70, 72 and apertures 71 and 73 is measured through the center of the shaft 37, while in Fig. 7 the distance is determined on the same side of the shaft 37. a The operation is as follows: The motorgenerator G is brought up to suitable speed by any suitable means such for example, as illustrated in Fig. 1. There are impressed upon the slip rings 10 and 11 two complete cycles of electro-motive-force for each rev olution of the armature A, this difiering from the arrangement of Fig. 1 where there is one cycle of alternating electro-motiveforce for one revolution of the armature A. Contacts 46 and 47 cause passage of cur-.v rent through the primary P in the same direction, while the two contacts 50, 56 cause passage of current through the primary P in opposite direction. Here again only a part of each current'wave is utilized, for example, an extent indicated in. Fig. 2. The. secondary S delivers, for each revolution of the armature A, two impulses in one direction and two impulses in the other iso direction, but the cross-connectors 64, 65,

the double target or anode 63 is maintained positive, and the passage of energy occurs first from the double anode 63 to cathode 61, and then to cathode 62, resulting in the production of X-rays from the two anodes or targets alternately. The observer places his eyes in position so that first aperture 7 0 comes in front of his left eye, then aperture 71 comes in front of his right eye, then aperture 72 comes in front of his left eye and then aperture 73 comes in front of his right eye, each eye seeing the fluorescent screen twice for each revolution of the shaft 23. The principle is the same as that of Fig. 1 in that the non-registering images produced by the two anodes are viewed alternately by the eyes of the observer, and the object is seen stereoscopically. Here again the first resistance l9 controls the energy flowing between one anode and its cathode while the resistance 52 controls the energy flowing between the other anode and its cathode, the purpose of these resistances being the same as that described in connection with Fig. 1.

While we have shown Within the single tube X the double anode and the two cathodes it .is to be understood that one anode and its cathode may be in one tube, and the other anode and its cathode in a separate tube. In either case the two anodes or the two cathodes are permanently connected together. This is different from Fig. 1 and Fig. 3 where one cathode is permanently connected with one anode.

In Fig. 9 there is shown a system similar to that shown in Fig. 1, in that a two pole generator is employed and no rectification occurs. The generator, primary of the transformer and commutator, etc., are omitted from Fig. 9, being understood to be the same as or equivalent to those shown in Fig. 1. However the secondary S is shown and its one terminal'is permanently connected to the two points or contacts 7 4, 74 disposed opposite each other and connected to each other. The other terminal of the secondary S connects with the anode 32 of tube X and with cathode 31 of tube X The cathode 30 of tube X connects with point or contact 75, while the anode 33 of the tube X connects with point or contact 76 diametrically opposite to point or contact 75, the contacts 75 and 76 being disosed at right angles to The disk 77 of insulating material carries the aluminum or other conducting are 78 of substantially 180 extent. This is rotated by shaft 27 in synchronism with shaft 23 so that X-rays are produced alternately by the tubes X and X In' Fig. 10 an arrangement is shown where no rectification occurs but where a four pole generator is assumed. Here the disk carrles two aluminum or conducting the contacts 74, 74:.

arcs 79 and 80, diametrically opposed and each of substantially 90 extent. By this arrangement the tubes X and X are excited alternately, but each is excited twice for each revolution of the armature of the generator. In all cases where the apparatus is to be used for stereoscopy the targets or anodes, whether in the same or separate tubes, are placed substantially two and onehalf inches apart, the distance between the human eyes.

By the arrangement shown in Fig. 1 there is one mechanical cycle for one electrical cycle. The same is true of Fig. 9. In Fig. 6 there are two electrical cycles for one mechanical cycle, and the same is true of Fig. 10.

It is to be understood that our apparatus is not limited to stereoscopy, but may be used for any purpose where X-rays are to be produced alternately from different targets or anodes whether in the same or separate tubes. Thus our apparatus may be used for the X-ray treatment of tobacco or other materials or substances, in which case however separate tubes are preferable for the reason that when excited alternately the tube not being excited can radiate heat generated in it before its next excitation, and liberate so much of such heat as will allow its continuous use in the system without attaining a dangerousover temperature.

It is to be understood that our invention is not limited to the use of such portion of a current Wave as indicated in Fig. 2, for it is within our invention to use a greater or smaller fraction of a current wave or impulse. And it is to be understood that our invention is not limited to the use of amotor-generator as described, for we may use any other means for producing the current supplied to the transformer, such as an alternating current generator driven by electric motor.-

A synchronous alternating current motor may be used in place of machine G, in which case the conductors attached to brushes 12 and 13 connect with the source of alternating current, but the commutator in the primary circuit of the transformer and the members 26, 37, and 68 are coupled to or driven in definite relation with respect to the rotating member of the synchronous motor. The reversing switches 14 serve to reverse the direction of energy flow between anodes and cathodes, should the direction of flow be wrong for any reason.

NVhat we claim is:

1. The combination with a source of alternating current, of a step-up transformer, a commutator operating in synchronism with said current, resistance associated with said commutator in the primary circuit of'said transformer, a plurality of X-ray tubes, and a switch moving in synchronism with said alternating current intervening between the secondary of said transformer and said'X- ray tubes for bringing said X-ray tubes alternately into circuit with said transformer secondary.

2. The combination with a source of alternating current, of a step-up transformer. a commutator operating in synchronism -with said current, resistance associated bringing said pairs of cathodes and anodes alternately into circuit of the secondary of said transformer, a commutator operating in synchronism with said alternating current, branches inthe primary circuit of sald transformer, and resistances in said branches, said commutatorwpassing energy from the positive waves of said source of current through one of said branches and energy from the negative waves of said source. of current through the other of said branches.

4. The combination with a source of alternating current, of a step-up transformer, a commutator operating in synchronism with said alternating current, means associated with said commutator in the primary circuit of said transformer for adjusting the relative strengths of the positive and negative currents passed through the transformer primary, a plurality of pairs of X- ray cathodes and anodes, and switching.

mechanism operated in synchronism with said alternating current for closing the sec.

ondary circuit of said transformer alternately through the different pairs of cathodes and anodes.

5. The combination with a source of alternating current, a step-up transformer, a commutator operating in synchronism with said alternating current, the primary circuit of said transformer having branches controlled by said commutator and traversed respectively by positive and negative currents,.means for adjusting the strengths of said positive and negative currents independently of each other, a plurality of pairs of X-ray cathodes and anodes, and switching mechanism for closing the secondary circuit of said transformer through said pairs of cathodes and anodes alternately.

6. The combination with a source of alters nating current, a step-up transformer, a

commutator operating in synchronism with said alternating current, the primary circuit of said transformer having branches controlled by, said commutator and traversed respectively by positive and negative currents, means for adjusting the strengths of said positive and negative currents independently of each other, a plurality of pairs of X-ray cathodes and anodes, and a rectifying switch driven in synchronism with said alternating current intervening between said pairs of cathodes and anodes and the secondary of said transformer.

7. The combination with a source of alternating current, of a step-up transformer, a

commutator operating in-synchronism with said alternating current, said commutator passing positive current through one transformer primary circuit and negative current through another transformer primary circuit, means for controlling the strengths of either of said currents independently of the other, a plurality of pairs of X-ray cathodes and anodes, and switching mechanism operating in synchronism with said alternating current for bringing said pairs ofcathodes and anodes successively into circuit with the secondary of said transformer.

8. The combination with a source of alternating current, of a step-up transformer. a

commutatoroperating in synchronism with said current, resistance associated with said commutator in the primary circuit of said transformer, a plurality of X-ray tubes, a switch operating in synchronism with said alternating current intervening between the secondary of said transformer and said X- ray tubes for bringing said X-ray tubes alternately into circuit with said transformer secondary, a shutter operating in synchronism with said alternating current, and a fluorescent screen intervening between said X-ray tubes and said shutter.

9. The combination with a source of al ternating current, of a step-up transformer, a commutator operating in synchronism with said current, resistance associated with said commutator in the primary circuit of said transformer, a plurality of pairs of X-ray cathodes and anti-cathodes, a cathode and an anti-cathode connected to one terminal of the secondary of said transformer.

a switch operating in synchronism with said synchronism with said alternating current for bringing said pairs of cathodes and anticathodes alternately into circuit of the secondary of said transformer, a commutator operating in synchronism with said alternating current, branches in the primary circuit of said transformer, resistances in said branches, said commutator passing energy from the positive waves of said source of current through one of said branches and energy from the negative waves of said source of current through the other of said branches, a shutter operating in synchronism with said alternating current, and a fluorescent screen intervening between said anti-cathodes and said shutter.

11. The combination with a source of alternating current of a step-up transformer, a commutator operating in synchronism with said" alternating current, means associated with said commutator in the primary circuit of said transformer for adjusting the relative strengths of the positive and negative currents passed through the transformer primary, a plurality of pairs of X-ray cathodes and anti-cathodes, switching mechanism operated in synchronism with said alternating current for closing the secondary circuit of said transformer alternately through the different pairs of cathodes and anti-cathodes, a shutter operating in synchronism with said alternating current,iand a fluorescent screen intervening between said anti-cathodes and said shutter.

12. The combination with a source of alternating current, a step-up transformer, a commutator operating in synchronism with said alternating current, cuit of said transformer having branches controlled by said commutator and traversed respectively by rents, means for adjusting the strengths of said positive and negative currents independently of each other, a plurality of pairs of X-ray cathodes and anti-cathodes, switching mechanism for closing the secondary circuit of said transformer through said pair of cathodes and anti-cathodes alternately, a shutter operating in synchronism with said alternating current, and a fluorescent screen intervening between said anti- ,cathodes and said shutter.

13. The combination with a source of alternating current, a step-up transformer, a commutator operating in synchronism with said alternating current, the primary circuit of said transformer having branches controlled by said commutator and traversed respectively by positive and negative ourrents, means for adjusting the strengths of --said positive and negative currents independen'iiy of each other, a plurality of pairs of X-ra-y cathodes and anti-cathodes, a rectifying switch driven in synchronism with said alternating current intervening bethe primary cir-' positive and negative curtween said pairs of cathodes and anticathodes and the secondary of said transformer,'a shutter operating in synchronism with said alternating current, and a fluorescent screen intervening between said anticathodes and said shutter.

H. The combination with a source of alternating current, of a step-up transformer, a commutator operating in synchronism with said alternating current, said commutator passing positive current through one transformer primary circuit and negative current through another transformer primary circuit, means for controlling the strengths of either of said currents independently of the other, a plurality of pairs of X-ray cathodes and anti-cathodes, switching mechanism operating in synchronism with said alternating current for bringing said pairs of cathodes and anti-cathodes successively into circuit with the secondary of said transformer, a shutter operating in synchronism with said alternating current, and a fluorescent screen intervening between said anti-cathodes and said shutter.

15. The combination with a source of alternating current, of a step-up transformer, a commutator operating in synchronism with said alternating current, said commutator passing positive current from said source through one path and negative current from said source through another path, a plurality of pairs of X-ray cathodes and anodes alternately traversed by energy from the secondary of said transformer, and means associated with said commutator and said positive and negative current paths for adjusting the strengths of said positive and negative currents independently of each other.

16. The combination with a plurality of X-ray producers, of means for supplying high tension uni-directional current to said X-ray producers, a source of low tension current from which said high tension current is derived, and means in the circuit of said low tension'source controlling energy delivered to one of said X-ray producers independently of the energy delivered to another of said X-ray producers.

17 The combination with a source of alternating current, of a transformer, a

included in different paths in a secondary circuit of said transformer, commutating mechanism in the primary circuit of said transformer, and current restraining means associated with said commutating mechanism in the primary of said transformer for controlling the energy of one of said paths independently of another of said paths.

18. The combination with a source of current, of a commutator and cooperating cir-' cuit branches, a transformer whose primary circuit is controlled by said commutator, a,

plurality of pairs of X-ray cathodes and anodes plurality of pairs of cathodes and anodes,

. means for bringing said pairs of cathodes and anodes successively into communication with the secondary circuit of said transformer, and current restraining means in said circuit branches in the primary circuit of said transformer for controlling the energy delivered to one pair of cathodes and anodes independently of another pair.

19. The combination with a source of current, of a transformer, a plurality of pairs of X-ray cathodes and anodes deriving energy from the secondary of said transformer, the primary circuit of said transformer having a branch for each of said pairs of cathodes and anodes, current restraining means in each of said branches, and a commutator for delivering energy to the primary of said transformer through said branches in succession.

20. The combination with a plurality of X-ray producers, of means for delivering high tension uni-directional current to said producers alternately, a source of low tension current from which said high tension current is'derived, and means in the circuit of said low tension source for controlling the energy delivered to onevofsaid X-ray producers independently of the energy delivered to another of said X-ray producers.

21. 'The combination with a transformer, of a plurality of pairs of X-ray cathodes and anodes, means for bringing said pairs successively into communication with the secondary of said transformer, a source of current, means for passing current from said source in succession through differentpaths in the primary circuit of said transformer, and energy controlling means in each of said paths.

22. The combination with a transformer, of a plurality of pairs of X-ray cathodes and anodes, means fer bringing said pairs successively into communication with the secondary of said transformer, a source of current, a plurality of branches in the primary circuit of said transformer, energy controlling means in each of said branches, and commutating means delivering energy to said branches in succession and at the same rate of succession as of delivery of energy from the secondary of said transformer to said pairs of X-ray cathodes and anodes.

23. The combination with a plurality of pairs of X-ray cathodes and anodes, of a step-up transformer, a high potential rectifying switch for delivering energy to said pairs of cathodes and anodes, said anodes connected to inter-connected contacts of said rectifying switch, a source ofalternating current, a commutator and circuit branches in the primary circuit of said transformer, energy controlling means in said branches, and means for driving said rectifying switch and said commutator in synchronism with said alternating current.

24. The combination with a plurality of pairs of X-ray cathodes and anodes, of a step-up transformer, a high potential recti-- pairs of cathodes and anodes, a source of alternating current, a commutato; and circuit branches in the primary circuit of said transformer, energy controlling means in said branches, and means for driving said rectifying switch and said commutator in synchronism with said alternating current at the rate of two electrical cycles per mechanical cycle.

:26. The combination with a source of all ternating current, of a step-up transformer, a commutator and circuit branches in the primary circuit of said transformer, energy controlling means in said branches, a plurality of X-ray cathodes cooperating with anodes, a switch for bringing said cathodes successively into communication with the secondary of said transformer, a shutter, said commutator and said switch operating in synchronism with said alternating current at the rate of two electrical cycles mechanical cycle, said shutter having apertures for each eye of an observer, and means for driving said shutter in synchrenism with said current.

27. In apparatus of the character describedya rotary shutter having two oertures for each eye of an observer, the Jar 'tures for one eye being disposed. opp site to each other on a diameter, and the n tures for the other eye being disposed nnpcsite to each other on a diameter at angles to said first named diameter.

28. The combination with a plurality of paths each comprising a vacuum, of stepup transformer delivering energy to s "d paths, a source of current, a cor and circuit branches controlled there in primary circuit of said transformer, and energy controlling means in said circuit branches, whereby the energy delivered through one of said vacuum paths varied independently of the ens another of said paths.

29. The combination with a plura. y of paths each comprising vacuum, of stepup transformer, means for successivenecting said paths with said transiermer,

a source of alternating current, a commutator and circuit branches controlled thereby in a primary circuit of said transformer, and energy controlling means in said circuit branches, said first named means and said commutator operating in synchronism with said alternating current, whereby energy is pased successively through said circuit branches and successively through said vacuum paths and the energy in one of said vacuum paths controlled independently of the energy in another of said paths.-

30. The combination with a plurality of paths each comprising a vacuum, of a transformer, means for connecting said paths in succession with said transformer to receive energy therefrom, and means in the primary circuit of said transformer for controlling the energy delivered to one of said paths independently of the energy in another of said paths. 7

31. The combination with a lurality of X-ray cathodes'and anodes, of a step-up transformer, means for connecting said pairs of cathodes and anodes in succession with said transformer to receive energy therefrom, and means in the primary circuit of said transformer for controlling the energy deliverd to one of said pairs of cathodes and anodes independently of the energy delivered to another of said pairs.

32. The combination with a plurality of X-ray producers, of a transformer, means for connecting said X-ray producers in suecession with said transformer to receive energy therefrom, and means in the primary circuit of said transformer for controlling the energy delivered to one of said X-ray producers independently of the energy delivered to another of said X-ray producers.

38. The combination with a source of alternating current, of a transformer, a plurality of X-ray producers, a switch operating in synchronism .with said current for connecting said X-ray producers in succession with said transformer, and means in the primary circuit of said transformer for controlling the energy delivered to one of said X-ray producers independently of the energy delivered to another of said X-ray producers.

34. The combination with a source of alternating current, of a transformer, a plurality of X-ray producers, a switch operating in synchronism with said current for connecting said X-ray producers in succession with said transformer, means in the primary circuit of said transformer for controlling the energy delivered to one of said X-ray producers independently of the energy delivered to another of said X-ray producers, and a shutter operating in synchronism with said current.

35. The combination with a source of alternating current, of a transformer. a plurality of X-ray producers, a switch operating in synchronism with said current connecting said X-ray producers in succession with said transformer, a commutator operating in synchronism with said current, the primary circuit of said transformer having branches controlled by said commutator, and energy controlling means in said branches.

36. The combination with a source of alternating current, of a transformer, a plurality of X-ray producers, a switch operating in synchronism with said current connecting said X-ray producers in succession with said transformer, a commutator operating in synchronism with said current, the primary circuit of said transformer having branches controlled by said commutator, energy controlling means in said branches, and a shutter operating in synchronism with said current.

In testimony whereof we have hereunto aiiixed our signatures at the city of Philadelphia, State of Pennsylvania, this tenth day of August, 1912, in the presence of the two subscribin witnesses.

H6MER CLYDE SNOOK. EDWIN W. KELLY. Witnesses:

E. T. MCCALL, BEATRICE WHITNEY. 

